Patent GB-310288-A (GB)
IPC: B23B47/22
Filed: 1928-06-26
Abstract: 310,288. National Automatic Tool Co., (Assignees of Galloway, R.. M., and Schafer, R. A.). Dec. 2, 1927, [Convention date]. Divided on 301,481. Drilling-machines.-A machine tool having a moving part which performs a cycle of movements and then comes to rest has a hydraulic feed for the movable part, the supply of fluid to the cylinder being controlled by a valve which is moved against a constant pressure to initiate a cycle and is then allowed to return in stages to one of a number of neutral positions, in each of which no fluid is admitted to the cylinder. In one form of machine a vertical column 69, Fig. 4, supports a vertically adjustable work-table 70 and a vertically moving tool-head 72, the tool spindle 75 being driven by gearing in a stationary box 71 and a belt 74 from an electric motor 73, a clutch 76a for the belt drive being hand controlled at 76. The fluid pressure cylinder is attached to the toolhead and its piston rod 14 is attached to the stationary box 71. A pump 77, driven by the spindle driving gear, draws fluid by a pipe 79 from a reservoir and supplies it by a pipe 78 to the distributing valve 94, a relief valve and overflow pipe 81 leading back to the reservoir, together with the exhaust, 80 from the cylinder. The piston 96, Fig. 8, of the distributing valve is attached to a rod 83 which is normally pressed downwards by a spring 89a Fig. 4, and may be raised to its extreme upper position by a hand lever 91 and locked there by a spring trigger 85 engaging a stepped dog 84 on the valve rod. In operation, after the piston 96 has been raised by hand, fluid is admitted from the pipe 78 to the pipe 98 through both sets of ports 98<a>, 98<b>, causing the tool-head to be fed rapidly towards the work. When a dog 88 on the head encounters the trigger 85 the valve is allowed to drop till the trigger engages the next step 84, in which position the port 98<a> is cut off and the head receives a slow cutting feed. At the end of the working stroke the dog 89 encounters the trigger and the valve is moved to cut off the port 98<b>, connect the port 98<a> to exhaust through a port 103 in the valve, and connect the pipe 99 to the supply for a rapid upward traverse of the tool-head. When the head reaches its upper limit the dog 87 encounters the trigger and allows the valve 96 to move to one of two extreme positions, in one of which the supply pipe 78 is completely cut off and the pump 77 delivers to the reservoir against the head of the relief valve, whilst in the other (lower) position the pipe 78 is connected through the port 103 to exhaust without restriction. The lower position is utilized when the tool-head has to remain in its upper inoperative position for considerable periods while the work is being changed, and the final position of the valve is determined by adjustment of the collar 90, Fig. 4, on the valve rod; by adjustment of the length of the dog 87 to govern the number of steps 84 which may pass the trigger, or by an adjustable screw in the end of the valve casing 94. An emergency release is provided by a hand operated plunger 86 which may be depressed to allow the valve 96 to move to its return position, this position being indicated by marks on the plunger or by a spring-pressed trigger engaging a notch therein. In another form of drilling-machine, a unit comprises a bed 4, Fig. 2, capable of being secured in any position on a frame and supporting a slidable drill-head 3 carrying an electric motor 6 and two parallel drill spindles 9 driven through gearing 8 and a flexible coupling 11 from the motor.. A hydraulic cylinder 5 is formed integral with or is attached to the head and cooperates with a piston 15 on a rod 14 secured to a bracket 2 on the bed 4. Fluid is supplied by a pump from a reservoir to the inner side of the piston by a pipe 17, the hollow piston rod and ports 18 and to the outer side by pipes 19, 20, the pipes 17, 20 being connected to a reciprocating piston valve 22. The rod 25 of the valve carries a piston 44 working in a pneumatic cylinder 43 and serves for setting the valve while a spring 40 normally tends to move the valve to the right in Fig. 2 but is prevented from operating by an L-shaped latch 27 normally forced upwards by a spring so as to engage one of a series of steps 62 on a stop 28 attached to the valve rod 25. A pair of plungers 29 are adapted to depress the latch when engaged by dogs 33, 34, 35 adjustably secured to the drill head so as to allow the spring 40 to move the piston valve in stages. The valve 22, Fig. 5, carries a supply pipe 48 leading from the pump, an exhaust pipe 47 leading to the reservoir and the pipes 17, 20 leading to the opposite ends of the cylinder 5. An adjustable auxiliary valve 54 has an elongated port 58 connecting a port 52 in the valve liner 23 to the pipe 20. In operation, air is admitted by a hand operated valve to the cylinder 43, moving the valve 24 to the left in Fig. 5, and allowing pressure fluid to proceed by both of the ports 49, 52 to the outer end of the cylinder 5 to cause a rapid advance of the tool-head 3 and connecting the pipe 17 to exhaust. When the drills are almost in contact with the work the dog 34 depresses one of the plungers 29 and allows the valve 24 to move a distance equal to one of the notches, 62, Fig. 2, in which position (shown d6tted in Fig. 5) fluid is supplied to the cylinder by the port 52 only so as to give a slow cutting feed to the tool-head. On completion of the working operation the dog 35 depresses a plunger 29, thereby cutting off the supply to the pipe 20, connecting the port 49 to exhaust and connecting the pipe 17 to the supply so that the tool-head may be retracted rapidly. In the rearmost position of the tool-head the dog 33 depresses the second plunger 29, thus allowing the valve 24 to assume its extreme right hand position, in which position the supply from the pipe 48 is completely cut off. The tool-head thereupon remains at rest until the piston 44 is again actuated by the hand-controlled valve. In order to return the tool-head to its retracted position at any intermediate point of its cycle, reverse movement of the hand controlled valve admits air to a vertical cylinder having a plunger engaging the trigger 27 to depress the latter and allow the valve 24 to assume the return position. The valve 22 of the drill unit shown in Fig. 2 may also be provided with two final or neutral positions, the one which cuts off the supply from the pump completely being used when the unit forms one of a number which may be secured in any relative positions and are supplied from the same pump, while the position which connects the supply directly to exhaust is used when the unit is employed by itself. The determination of the final valve position is effected by adjustment of the collar 42, adjustment of the length of the dog 33 or change of the dog 28, whilst the valve may be changed readily for one of different type.